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Chemoattraction
Chemotaxis (from '' chemo-'' + ''taxis'') is the movement of an organism or entity in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food (e.g., glucose) by swimming toward the highest concentration of food molecules, or to flee from poisons (e.g., phenol). In multicellular organisms, chemotaxis is critical to early development (e.g., movement of sperm towards the egg during fertilization) and development (e.g., migration of neurons or lymphocytes) as well as in normal function and health (e.g., migration of leukocytes during injury or infection). In addition, it has been recognized that mechanisms that allow chemotaxis in animals can be subverted during cancer metastasis. The aberrant chemotaxis of leukocytes and lymphocytes also contribute to inflammatory diseases such as atherosclerosis, asthma, and art ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemotaxis Assay
Chemotaxis assays are experimental tools for evaluation of chemotactic ability of prokaryotic or eukaryotic cells. A wide variety of techniques have been developed. Some techniques are qualitative - allowing an investigator to approximately determine a cell's chemotactic affinity for an analyte - while others are quantitative, allowing a precise measurement of this affinity. Quality control In general, the most important requisite is to calibrate the incubation time of the assay both to the model cell and the ligand to be evaluated. Too short incubation time results in no cells in the sample, while too long time perturbs the concentration gradients and measures more chemokinetic than chemotactic responses. The most commonly used techniques are grouped into two main groups: Agar-plate techniques This way of evaluation deals with agar-agar or gelatine containing semi-solid layers made prior to the experiment. Small wells are cut into the layer and filled with cells and the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kinesis (biology)
Kinesis, like a taxis or tropism, is a movement or activity of a cell or an organism in response to a stimulus (such as gas exposure, light intensity or ambient temperature). Unlike taxis, the response to the stimulus provided is non-directional. The animal does not move toward or away from the stimulus but moves at either a slow or fast rate depending on its "comfort zone." In this case, a fast movement (non-random) means that the animal is searching for its comfort zone while a slow movement indicates that it has found it. Types There are two main types of kineses, both resulting in aggregations. However, the stimulus does not act to attract or repel individuals. Orthokinesis: in which the speed of movement of the individual is dependent upon the stimulus intensity. For example, the locomotion of the collembola, '' Orchesella cincta'', in relation to water. With increased water saturation in the soil there is an increase in the direction of its movement towards the aimed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Random Walk
In mathematics, a random walk is a random process that describes a path that consists of a succession of random steps on some mathematical space. An elementary example of a random walk is the random walk on the integer number line \mathbb Z which starts at 0, and at each step moves +1 or −1 with equal probability. Other examples include the path traced by a molecule as it travels in a liquid or a gas (see Brownian motion), the search path of a foraging animal, or the price of a fluctuating stock and the financial status of a gambler. Random walks have applications to engineering and many scientific fields including ecology, psychology, computer science, physics, chemistry, biology, economics, and sociology. The term ''random walk'' was first introduced by Karl Pearson in 1905. Lattice random walk A popular random walk model is that of a random walk on a regular lattice, where at each step the location jumps to another site according to some probability distribution. In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Julius Adler (biochemist)
Julius Adler Ph.D. (born 1930) is an American biochemist. He has been an Emeritus Professor of biochemistry and genetics at the University of Wisconsin–Madison since 1997. Early life Adler was born in Edelfingen, Germany in 1930. He came to the United States in 1938 at the age of 8 and became a naturalized citizen in 1943. His family settled in Grand Forks, North Dakota where their relatives were among the first Europeans to arrive in 1880. Since he was child, Adler had been fascinated by how organisms sense and respond to the environment. Education Adler attended Harvard University and received his A.B. in Biochemical Sciences in 1952. He then studied with Henry A. Lardy at the University of Wisconsin–Madison and earned an M.S. in Biochemistry in 1954 and a Ph.D. in Biochemistry in 1957. After graduating, Adler did postdoctoral fellowships with Arthur Kornberg in the Department of Microbiology at Washington University School of Medicine (1957–59) and A. Dale Kaiser in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Henry Harris (scientist)
Sir Henry Harris (28 January 1925 – 31 October 2014) was an Australian professor of medicine at the University of Oxford who led pioneering work on cancer and human genetics in the 2000s. Early life and education Harris was born in 1925 to a Jewish family in the Soviet Union. In 1929, his family emigrated to Australia.''The Guardian'' Retrieved 11 December 2014 Harris studied at from 1937 to 1941. In 1941, he first read , but was subsequently attracted to medicine through his literary interests. He studi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phagocytosis
Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is called a phagocyte. In a multicellular organism's immune system, phagocytosis is a major mechanism used to remove pathogens and cell debris. The ingested material is then digested in the phagosome. Bacteria, dead tissue cells, and small mineral particles are all examples of objects that may be phagocytized. Some protozoa use phagocytosis as means to obtain nutrients. History Phagocytosis was first noted by Canadian physician William Osler (1876), and later studied and named by Élie Metchnikoff (1880, 1883). In immune system Phagocytosis is one main mechanisms of the innate immune defense. It is one of the first processes responding to infection, and is also one of the initiating branches of an adaptive immune response. Although m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Élie Metchnikoff
Ilya Ilyich Mechnikov (russian: Илья Ильич Мечников; – 15 July 1916), also spelled Élie Metchnikoff, was a Russian zoologist best known for his pioneering research in immunology. Belkin, a Russian science historian, explains why Metchnikoff himself, in his Nobel autobiography – and subsequently, many other sources – mistakenly cited his date of birth as 16 May instead of 15 May. Metchnikoff made the mistake of adding 13 days to 3 May, his Old Style birthday, as was the convention in the 20th century. But since he had been born in the 19th century, only 12 days should have been added. He and Paul Ehrlich were jointly awarded the 1908 Nobel Prize in Physiology or Medicine "in recognition of their work on immunity". Mechnikov was born in modern-day Ukraine to a Romanian noble father and a Ukrainian-Jewish mother, lived and worked for many years on the territory of what was then the Russian Empire, and later on continued his career in France. Given this ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ciliate
The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different undulating pattern than flagella. Cilia occur in all members of the group (although the peculiar Suctoria only have them for part of their life cycle) and are variously used in swimming, crawling, attachment, feeding, and sensation. Ciliates are an important group of protists, common almost anywhere there is water—in lakes, ponds, oceans, rivers, and soils. About 4,500 unique free-living species have been described, and the potential number of extant species is estimated at 27,000–40,000. Included in this number are many ectosymbiotic and endosymbiotic species, as well as some obligate and opportunistic parasites. Ciliate species range in size from as little as 10 µm in some colpodeans to as much as 4 mm in length in some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Herbert Spencer Jennings
Herbert Spencer Jennings (April 8, 1868 – April 14, 1947) was an American zoologist, geneticist, and eugenicist. His research helped demonstrate the link between physical and chemical stimulation and automatic responses in lower orders of animals. Life He was born in Tonica, Illinois, on April 8, 1868, the son of George Nelson Jennings and his wife Olive Taft Jenks. He studied at the University of Michigan graduating BS in 1893 then Harvard University where he gained a further AM degree in 1895 and a PhD in 1896. In 1906 he began a long and illustrious career at Johns Hopkins University in Baltimore where he stayed until retirement in 1938. He married twice: firstly in 1898 to Louisa Burridge and secondly in 1939 to Lulu Plant. He died in Santa Monica, California, on April 14, 1947. He is buried in Forest Lawn Memorial Park in Glendale. Career Tracy Sonneborn would later write:Jennings was so struck by the continued production of hereditarily diverse clones at conjugation, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wilhelm Pfeffer
Wilhelm Friedrich Philipp Pfeffer (9 March 1845 – 31 January 1920) was a German botanist and plant physiologist born in Grebenstein. Academic career He studied chemistry and pharmacy at the University of Göttingen, where his instructors included Friedrich Wöhler (1800-1882), William Eduard Weber (1804-1891) and Wilhelm Rudolph Fittig (1835-1910). Afterwards, he furthered his education at the universities of Marburg and Berlin. At Berlin, he studied under Alexander Braun (1805-1877) and was an assistant to Nathanael Pringsheim (1823-1894). Later on, he served as an assistant to Julius von Sachs (1832-1897) at Würzburg, In 1873 he was appointed professor of pharmacology and botany at the University of Bonn, followed by professorships at the Universities of Basel (from 1877) and Tübingen (from 1878), where he also served as director of the Botanischer Garten der Universität Tübingen. In 1887 he became a professor at the University of Leipzig and director of its botanical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
